I'm 16 years old and 5 weeks ago i found a hard lump in my groin, it is the size of a grape and has grown recently?

Lymph node: The body has a series of strainers called lymph nodes that sift through stray fluids in the body & take out germs and other debris.You likely have & have had something going on with that leg,a series of bug bites or a sore, that led to the enlargement. These usually enlarge & shrink over 3-4 wks. If this has gone on 5 wks you may want your doc to confirm the process.