Canker Sore

My 19 year old son developed a canker sore on the inside of his lower lip approximately three weeks ago. Canker sores are not out of the ordinary for him. However when this one healed it left a hard bump of the same size where the canker sore was. It's not painful but it was a rather larger canker sore so the bump is also rather large. It's similar to a hard blister or soft wart. Is this anything to be concerned about? I've just never seen a canker sore do this before.

[Jerome Tsang, DDS]

How large was the size of the canker sore?  It may have been what is called a major aphthous ulcer and can result in some scarring of the tissue.  I'm not aware of any treatment that is needed for the scarring.  You may want to post this question in the Oral and Maxillofacial Surgery section to ask the oral surgeon if removal of the scar tissue is necessary.  Best wishes.