Tricep Injury - HELP!!!!

Everytime i surf for longer than 2 hours, afterwards, i have a nasty knot in my left tricep & its driving me crazy as i cant lift the arm horizontally upwards without pain.
I condition train in the gym 4 nights a week - focusing heavily on rotator cuff conditioning & tricep endurance, and stretch thoroughly before & after every surf as well as swimming regularly.
The problem has been there for nearly a year now - a deep massage to rub the knot out always seems to work & by the evening of the next day, the pain & movement restriction is gone - but then the next time i surf - it returns.
I live in africa, so getting good professional advice on this is difficult.
I feel the pain in the side deltoid (not sure of the correct medical term for this), yet after warming the tricep up with a massage - i can feel the knot. After 20 minutes of massage & incredible pain - the knot is slowly massaged out & by the next day the problem/pain/restriction is gone.
I would be interested to know if anyone else has/had this problem - & if so how they got rid of it.
I condition train in the gym 4 nights a week - focusing heavily on rotator cuff conditioning & tricep endurance, and stretch thoroughly before & after every surf as well as swimming regularly.
The problem has been there for nearly a year now - a deep massage to rub the knot out always seems to work & by the evening of the next day, the pain & movement restriction is gone - but then the next time i surf - it returns.
I live in africa, so getting good professional advice on this is difficult.
I feel the pain in the side deltoid (not sure of the correct medical term for this), yet after warming the tricep up with a massage - i can feel the knot. After 20 minutes of massage & incredible pain - the knot is slowly massaged out & by the next day the problem/pain/restriction is gone.
I would be interested to know if anyone else has/had this problem - & if so how they got rid of it.