Pimple-like eruption on my second toe - synovial fluid? Previously treated with steroid injection - it's back - treatment?

Sounds like. a mucous cyst. These are small cysts over a joint which is filled with synovial or joint fluid. Steroid injections may help. In recurring or painful ones, sometimes surgery which includes addressing the affected joint is necessary. See Podiatrist for examination and discussion.
Synovial fluid? Were you told that it is synovial fluid? Is it painful? How long have you had it? Typically I would not think a pimple-like lesion on a toe would be very serious as long as you don't have diabetes or something else to suppress your immune system. .
Was it like jello? if yes then its a digital mucous cyst and can recur if attached to joint space, need xray to determine if injections will work.