I agree. You should see a doctor and if need be ask him to refer you to an orthopedic specialist, preferably one with expertise in sports injuries. The sooner you take care of that, the better you’ll be when you return to action on the mound.
After the 1951 World Series, in which Ed Lopat had won both games he had pitched, he suddenly could not lift his left arm (the weather might have been a factor; it was cold and damp all through the Series). The doctors could not figure out what was wrong with him, and for the first part of the 1952 season he was on the shelf, which he didn’t like at all because what he wanted to do was get out there and pitch! But one day he remembered an orthopedic surgeon in Chicago, a guy he had known in his White Sox days, and he flew out to see him. This doctor examined Lopat and told him that he had tendonitis in his left shoulder, and then he prescribed a treatment which we might call bizarre these days—a series of ten X-rays, which is not used any more. But this worked, and when Lopat came off the DL he was pitching better than ever; from that point till the end of the 1954 season he ran up a record of 33-8, and the 1953 season found him with a 16-4, .800 record and a league-leading ERA of 2.42.
So, if your arm is really bothering you, see a doctor and take care of the problem!