Hello,
Yes it is normal for a bum to form under the scar site because of fibrous tissue formation during wound healing. This should gradually go away and no specific treatment is required. If however there is any growth on the outside then the possibility of keloids has to be ruled out.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.