Can be just simply mild trauma with netting & transport... The odd bit of blood under a scale usually means nothing & I'd just observe. Good clean water is usually all you need.
If it is actually an open wound or a sore, treatment would be needed. I would just start with a bit of salt (0.1-0.3%) in the tank, and if the fish is big enough to handle, a bit of anti-biotics ointment over the sore (betadine ointment is usually recommended for open sores in golds, but other people had used polysporin & such).
If you see red veins at the base of the fins, or more sinister, lots of bleeding under the chin & face (costia), and or behaviour changes, then I'd consider sepsis & try antibiotic food.
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.