Thanks for your query, I have gone through your query. The lump can be because of the infected wound site. The limited or difficulty in mouth opening can be because of the fibrosis of the wound during healing process. If the wound or cut is deep, it has to be closed by suturing layer by layer, i do not understand why it was not sutured. So consult a oral maxillofacial surgeon and get it evaluated. Mean while take a course of antibiotics like amoxicillin and metronidazole. I hope my answer will help you, take care.