How do i know if i just pulled a muscle or something in my right arm?

First is trauma then: Pain. Then it's a matter of degree.1= minor, no major tear. Recovery is rest activity modifications. 2= tearing of some muscle fibers,swelling, hematoma tho not massive.3= disruption of the muscle at it's attachment or mid body tears massive swelling. Larger hematoma that follows tissue plains & will spread to the elbow just do to gravity. Long recovery,? surgery,lots of rehab under MD care.