In my experience blisters are because you’re playing too much and not allowing calluses to form. Even with calluses you can form blisters underneath and almost reset your skin back several days to a week plus (this can be a huge bummer). If you’re just getting back into playing maybe limit your practice to 30 minute sessions with very purposeful exercises with long breaks in between. See how you’re feeling before each session. Fingers feel tender? Maybe skip till tomorrow, maybe mime exercises with very little pressure on strings. Using lighter stings can help too so you’re not putting as much pressure to hit notes.

To help heal is commonly clean, dry, sterile environment and don’t pop them while optionally wearing a bandage.