Welcome and thanks for posting your query to Healthcare Magic.
I can understand your concern for the lump and pain in the stitches.
Ther can be two possibilities for the condition you are facing. The one is simple pain at the injury
site because of nerve
regeneration. Whenever there is injury to skin the nerves also get injured. During the repair process of the nerves there is sharp shooting pain is felt by the patient at that local site.
The second possibility is of "foriegn body granuloma". This is formed due to the entrapment of some foriegn materiel such as dust particle or some thing related in the skin during repair process. This form s the lump kind of thing during healing process.
For the best of the possibility you meet a surgeon who can examine the area thoroughly and then advise you accordingly.
Above and all the conditions enumerated above are totally simple condition and can be treated easily.
Hope these informations will help.
"With good health wishes"
Dr Sanjay Kumar Kanodia
MD (Dermatology & STDs)