While working out at baseball training today, i think i might have pulled a chest muscle when pitching. how would i know?

Tenderness in area: Pulled muscles are very common, typically easily diagnosed on physical examination. There is usually tenderness over the muscle involved, discomfort with stretching of the muscle, possible weakness as well on strength testing or activities. Occasonally it can be associated with a 'pop' during the activity. Swelling, bruising, and sometimes a deformity can be seem on inspection as well.