Hi, i'm worried about syphillis. i had blood test after 4 weeks for syphillis which came back negative. but 6.5 weeks later noticed a sore in my nose.

Not syphilis: Syphilis is exceedingly unlikely, even if you were intimately exposed to a known infected person. I've never heard of a primary syphilis lesion involving the nose, and 6 weeks is too late; syphilis onset usually 10-20 days. To be even more certain, have another blood test now. The blood tests are conclusive anytime after six weeks. You can expect it to be negative.