It looks to me like a hypertrophic scar - glossy, non-scaley, macular lesion or lump, well rounded, without top of growth extending beyond its boundaries! The only worry is the location & almost near symmetric appearance!
Well, knuckle pads are a kind of Hypertrophic Scar (HT) - just a special type of HT with a special but layman's terminology - Histologically, it may be the same as HT; anatomically & etiologically, it may be different! Cheers!