Dear Buddy,
The nodule in the middle finger is resulting into Trigger Finger. The presence of nodule delays the movement of the tendons, hence we get this sort of condition where at later stage triggering occurs. For this condition, its better to opt for surgery and release the nodule, so that the triggering stops.
Getting a second opinion from Rheumatologist is one of the best things you have thought of.
There is no specific reason as why you have these small tumors/nodules OR why it happens on the left side only.I have got no explanations for this.
Regards.