I got a bad bug bite and dont know how to treat it theres no.visible entrance wound..help !!!!??

Ok so im in puerto rico now and I got a bug bite its red and swollen and sensitive to the touch on the top of my foot every time I walk or bend my foot it hurts

When I got the bite the bug was round n black but I couldnt tell what it was really but I ended up flinging it off out of disgust and squishing it :/ and I usually get mosquito bits but this really hurts and doesnt really ich anyone have any idea to treat it im desperate.here