scar-like tissue on knuckles

i have had this scar-like tissue on the index finger of my left hand knuckle for several months now. It's occasionally itchy like a rash, but doesn't appear like a normal rash i've seen. Its about 1.5 cm long and 0.5 cm wide. There is a similar spot on the knuckle of my left hand middle finger as well, but much smaller and less protruding. I was working as a dishwasher for quite some time and suspected that that was probably the cause, but i have since stopped and it doesnt seem to be getting better. I've also noticed some pimple like spots on the top of both hands, only about 3, which seem to disappear, but still seem strange. Any help would be great, thanks.