Help! Could I have psoriatic arthritis?

Hello! I have never had skin psoriasis - at least, I've had one small patch on my upper shoulder/neck area which could have been looking back, but apart from that, nothing. I do have type 1 diabetes, asthma, and eczema , among other things! However, I have had problems with my nails for some time - longitudinal ridges, breaking down the sides along the ridges, very brittle, a sort of line below the top of the finger where the bed looks pinker, slight lifting occasionally. Also, dents in the nail and little pits. One of my toes nails 9I think my toes are fins apart form this!) just came half off one day a couple of years ago, totally painlessly. There was no mould or any reason they could think of why this should happen. Starting lifting and they took the rest off. My GP sent a photo of my fingernails off to a dermatologist who said psoriasis. I have arthritis in one finger - my middle one on my left hand. the top joint is a little deformed by added bone now and looks to me as if it is beginning to lean left maybe only something i would notice! this joint hurts, and often underneath swells up in a little circle. At the minute it hurts just below and above the bottom of this joint. Sometimes it hurts all along this finger inside - sometimes it feels like bone, sometimes like it's a tendon. None of my problems are very severe - i've lost a toenail, but it doesn't inconvenience me, the nails are a real pain but I can live with it, but the arthritis worries me despite not being severe - for instance, my finger does not swell up into a sausage, it's just sore. Can you experts in this tell me whether this sounds like psoriatic arthritis, or does it sound like osteo? Should I get a referral, or should I wait until it becomes a worse problem? It does sound as if the fix could be worse than the problem unless you are very bad. Thank you.