I got bite 4 days ago on my elbow and it now swelling around it and is painful what it?

Insect bite?: I am assuming this was a bug of some sort, not a larger animal or human bite? If so, it may be just a reaction to the toxin in the insect bite. Try 1% hydrocortisone cream 2-3x/day, take an antihistamine like loratadine daily, apply cool compresses, and see if it improves over the next 2-3 days. If not, get in to be seen to make sure it is not an infection.