If it's truly minor use 1/4 cup of Epsom Salts (not like table salt) and bought at your drug store; add boiling water to dissolve and then add to tepid water (body temp). Soak a clean cloth and just take a little of the excess water out of it. Hold the abscess for 5 minutes or more (if the cat lets you). Take a towel a PAT DRY. DO NOT RUB! Do this 3 - 4 times a day. If it doesn't go away in 2 days please see your vet.