4 week old lump on forarm. This week.

My son had a red round area on his forearm and looked as if something had bitten as on close watch we found 2 small needle type holes in the area. On dermatologst visit he was prescribed fudic bnf cream and teczim syrup. The area of redness reduced and in 10 days a hard red lump developed in the area with mild pain and warm to the touch. The size of the lump didnt reduce in size. We then visited a surgeon who suggested that the area shud be cut open and any pus formed removed for quick healing. Other doctors whom we consulted suggest sarcaidosis , tb , antibioma . Its very confusing due to the different approaches of different doctor. Since last 3 weeks since the lump formation , i have been watching it day and night and to my naked eyes the size of the lump doesnt seem to have increased or decreased . It is around 2cm in length and 1 cm in breadth. Also attatched pictures taken this week.