Usually a sore feeling and then a blob of yellow pus under the skin. Get antibiotics fast at this stage to try and stop it developing further.
I get plenty of bumps and nodules from R's; my ulcers do start out that way, and then get inflamed /red or have a center that looks like a blister. I dab mine with hydrogen peroxide and apply nitro ointment...good luck
Mine start with pain and persistent blue colour. Always go to the doctor when you have an ulcer. If you have Raynaud and Scleroderma they don't heal by themselves because you don't have enough blood there to do the job. You may need antibiotics and Iloprost.
Are there any marks on the finger tip before the sore feeling, inflammation or pus? I have little red "marks" not like the "T" in CREST, which are all over my hands. These are larger. All of my finger tips are sensitive.
My two index fingers ulcerated almost down to the bone last year. Mine started off with a yellowish cast to the skin and then blood blisters popped up. When they ruptured, that was the beginning of a long journey of healing. A good strong anti-biotic cream is important. Some may take Bactroban, but I preferred Altabax. I have had two places that acted like they wanted to ulcerate and put Altabax on for a few days and it dried it up. Altabax will not build up resistance to bacteria in the skin. It took about 4 months for mine to completely heal. One of my doctors suggested filling in the sore that extended an entire joint with petroleum jelly every day so it won't dry out and it worked. Hope this helps.