Two things stand out right away when you mention blister using rings:
The first is the ring may be too skinny. The width of the ring tends to dig into your skin. This is more true when the ring is worn during pumping, not after pumping. As the skin plasticity (flexibility) increases, the loose skin wraps around or expand around the edge of the skinny
cock ring, causing friction and irritation. Not sure which ones you have. The
FatTires in MoS Shop may work better for you. Something with wider width to prevent the skin from digging in.
Second is the
cock ring materials. You got silicone, PTU rubbers, and various other blend. Possibly an allergic reaction to the material or the blend of plastic types?