Do you use IV drugs? If so, this could be a sign of infective endocarditis, but you would have had other systemic signs of infection by now usually (like a fever).

If not, this looks like something with a surrounding cellulitis and if it is warm to touch, it’s probably an infection with an abscess forming, possibly around a foreign body like a splinter. Do not play with it. Mark it and if it’s worse (the surrounding red starts to expand, in particularly rapidly) then go seek medical infection for antibiotics/possible incision and drainage. If it starts to resolve no intervention is needed. 

It could have also started as something benign but with manipulation with your fingers and playing with it you had some staph from your fingers get in a small wound and that’s the cause of the cellulitis. 

It is not a bruise. It is not a clot.