Rheumatoid arthritis can cause rheumatoid nodules. Fibromyalgia and myofascial pain syndrome don't have nodules or lumps associated with them.
However, lumps can be so many different things. They may or may not be associated with any of your diagnoses. Since they bother you, you should see your rheumatologist. He/she should be able to determine exactly what is causing them.
The lumps could indeed be a symptom of your RA, but they could also be something else. It's really important when you have a chronic illness to find a good doctor you trust and can contact when you have concerns. Early diagnosis and symptom relief can make a huge difference when it comes to staying active and feeling well.
A common tendency with RA and other autoimmune diseases is to attribute every symptom to the disease. I agree that the best course is to check with your doctor and let him/her have a look.