Pretty sure its a spider bite, after 3 weeks it still has a scab n is lightly red around scab, do i get it checked out or give it more time 2 heal?

Bite : If the area is becoming more red around the wound and or tender to touch (signs if infection) then see a dermatologist for proper diagnosis and treatment. A bite should heal within a few weeks.

Doubtful: True spider bites are very uncommon. More likely is a staphylococcal skin boil misinterpreted to be the bite of a spider. See a doctor and get this treated.