How long does it take for bump from spider bite to go away?

Depends on type of: Spider ; your sensitivity to it. Spider bites can have variable appearances. It might cause a pink or red bump with no symptoms. Or it could itch or be painful. Venomous spiders may cause significant pain radiating far from the site, cramping, sweating, necrosis of tissue or worse if there is an allergic reaction.

Nearly all bumps are: The brown recluse spider is not found in pennsylvania. Unless you saw and felt the spider attack you, then took it to an arachnologist for identification, assume it was not a spider bite. Spiders are plentiful everywhere but are completely harmless. Spider bites are rare, very painful, cause ulceration. If you have a "bump" it is something else.