Lump on chest

So my boyfriend came to me saying he had a pressure pain in his chest. Didn't radiate at all and no SOB. He pointed to around the left 4th intercostal area and said it hurt. I palpated over that area and felt a small lump. I compared it to the right and it was slightly different. I then percussed the left and right chest and it was general tympany up until the area he pointed to. It was clearly dull. I told him he should go to the doctor cause I'm barely in my first quarter of nursing school. I just said I definitely can tel there's something there. Can someone please give me an idea of what it could be? Then I can tell him and maybe it will convince him to go to the doctor.

As signs and symptoms go:

had a pressure type chest pain medial to 4th rib that increased upon palpation

he has chills and is warm to touch. I don't have a thermometer so I couldn't take his temp but he was warm to the touch and shivering. I said he may have a fever and he took Tylenol.