Firm(?) lump under the skin on one side of groin- hurts if i press on it too much. sometimes i feel a pulse from it. really freaked out it's metastatic cancer. any idea of what it could be?

Doctor can evaluate: Groin lumps can be caused by infected lymph nodes, enlarged non-infected lymph nodes, skin cysts, abscesses in the skin, etc... A bigger lump might even be a hernia. A primary care doctor can evaluate to see what it might be, and offer advice on treatment or testing. College-aged people rarely get cancer because they are still so young.