Theory:

It was Monday morning, Tom Sawyer, a student, did not feel comfortable. He was always like this on all the Monday mornings. The problem was he didn't like going to school. He always desired that there shouldn't be any holidays in between the week or he has to gain again the courage to go to the school, which is like a prison for him.
 
Tom was on his bed, and he did not get up yet for the school. He was trying to think if he had any physical problems or ailments so that he need not go to school. He looked at himself if he had any ailments like stomach ache, toothache, etc. But his stomach ache was not much, and after some time he did not feel stomach ache at all. But, one of his upper front teeth was hurting him. If he said that to his aunt, she would pull it out. So, he did not complain about that and kept it for future drama.
 
Suddenly, he remembered a doctor say that there is an illness that the patient has to be on the bed for two to three weeks or even lose a finger. Now he got something in his mind, he pulled his bed sheet and looked at his sore toe. He did not know the symptoms, neither he had any. He tried this trick and was making sound like he had lots of pain. Sid did not bother to look at him.
 
Tom was now overacting to get all the attention he can. He calmed down for some time and made more sound now and called out on Sid. Sid had to get up, he yawned and with his elbows got up. Tom continued his action.
 
Sid asked Tom what the matter was?  Sid is Tom's half brother, and he went near him and was keen on understanding what happened to Tom. Tom asked Sid not to shake him. Sid was worried if he needs to call aunt. Tom said that he would wait for some time, maybe his agony will reduce.
 
The sound made by Tom petrified Sid, and he asked him to stop and tell him till how long he was in pain? Tom replied for hours together, and not to make any movement as it is very painful.
 
Sid insisted that Tom should have waken him much earlier instead of suffering by himself.
 
Tom continued saying that he had forgiven Sid for all the mistakes he has done as he is going to die.
 
Sid was terrified as he felt something happened to Tom, and he is going to die.
 
Tom further advised Sid, to give away his window glass and his cat which had only one eye, to the new girl in the town.
  
Sid went to his aunt gathering his clothes. Tom was so much into it that his pain was feeling like truth. Sid went down and called out on aunt Polly saying Tom is going to die and asked her to come as soon as possible. Though aunt did not believe him, but still she ran upstairs with her lips trembling and face turning pale. Sid and Mary followed her as Mary is Tom's cousin. Aunt asked Tom what had happened. Tom replied his sore toe was dying.
 
The old lady took a breath; she consoled herself a little by laughing and crying. She turned to Tom and said she had almost fallen for it and that Tom should stop this and come out of the bed.
 
Tom felt stupid and said to Aunt Polly that it was his tooth which was paining.
 
Aunt Polly felt something was not right. She guessed that Tom was trying another trick. She asked him if he was pretending to have a toothache next.
  
Tom continued to say that the tooth was loose and painful.
  
By this time, Aunt Polly now understood everything. She asked Tom to stop crying and that he would not die out of toothache. She told Mary to get silk thread and some fire out of the kitchen so that she can pull the tooth out.
 
Tom knew that Aunt Polly understood his tricks and said that his toothache has gone and there is no need to pull the tooth out. He was also eager to go to school.
  
Aunt Polly made it clear to everyone that Tom was doing all these to stay home and go fishing. She suggested that Tom was taking advantage of her love. Meanwhile, she had everything to pull Tom's teeth out. She tied one end to Tom's teeth and another to the bedpost and slowly kept the fire near him. Before he could move, he saw his tooth loosely hanging.