hi,,thanks for the query
i like to know the duration of the pain,was it sudden or after an injury or lifting weights,do you have any neck pain
or giddiness when sitting in same posture,is the pain continuous or on and off,what aggravates the pain and releiving factors
do you feel any bruit(flow sensation in arm)..or
it can be muscle twist or sprain
do you have any weakness of rt hand loss of sensation or tingling
so you have to rule out spine problems,bone,muscle and nervous problem..and rule out av malformation (blood vessel condition)...
consult an orthopaedician,,get treated..