Although PsA is autoimmune based, I'm not sure it 'causes' SFN. I think more often, it accompanies other rheumatic disease process. Have you been tested for other Autoimmune diseases?? If not, this is certainly warranted.

I have PsA, but had Sjogren's first...and the Sjogren's is what caused my SFN/PN, not the PsA.

I'm also not sure you would be Dx with PsA with just psoriasis and joint pain. Typically, PsA involved major joint swellings and sausage like digits (fingers), confirmed fluid in the joints (even small joints of fingers), along with other signs of tendonitis (particularly Achilles) and flares of pain.

You should see a rheumatologist for a formal Dx, if this is what they think might be going on. A rheumatologist would also be the one to properly treat PsA, based upon severity.