Is It Safe To Take Advil To Treat Pain In Arm And Shoulder?

Hello,yesterday I had consulted a doctor near my local resident. I had an arm pain which I found out became a shoulder pain the following weekend. The doctor told me I had muscle spasms, and if the situation doesn t clear if I take my Advil Extra Strength [400] and if my arm forms rashes or blisters, to come back again as it seemed urgent. The next day (Today) my arm seems to have formed a few rashes and before tomorrow, I really would like some answers into what it could be.Thank you.