My son had a cyst undet his arm and he compressed it with warm to hot pressure, n it just popped n he gushed out blood, what does that indicate?

Abscess: What is sounds like he had was an abscess, which is a confined cavity filled with infected material, blood and pus. A warm compress often helps it come to a head and drain, after which it will likely heal. If it does not, see your doctor. Try not to squeeze these things; instead of rupturing outward, as your son's did, they can rupture inward, thus inadvertently spreading infection.