I usually just get a sterile needle and poke into it to let any pus drain out and then put chlorhexidine or Epsom salt soak on it. heals over for me in 2 days

Soak in hot-ish water to draw the pus to the surface and poke with sterile needle to drain.

ingrown finger nail probably. try soaking it a few times a day in warm water and epsom salt.

Once drained and opened though make sure to keep it clean!