First, know this is common. An erection is a normal physiological response caused by increased blood flow into the penis. Most unwanted erections go away on their own. Below are safe, practical steps you can try, plus signs that mean you should get medical help.

Immediate, non-sexual things to try

• Relax and breathe: Sit or lie down, take slow deep breaths for a few minutes. Calm, slow breathing helps reduce general arousal.
• Distract your mind: Think about something non-sexual and engaging (math problems, a task list, a neutral lecture). Mental distraction often helps the erection subside.
• Change position or clothing: Stand up, adjust or pull clothing so the penis is positioned comfortably and not pressed. Wearing tighter underwear or pulling the penis down between your legs can make it less obvious and more comfortable until it goes down.
• Cold compress or shower: A cool (not freezing) shower or a cold pack wrapped in a cloth on the lower abdomen/inner thighs for a minute can help constrict blood vessels and speed detumescence.
• Move your body: Light exercise such as a brisk walk, jogging in place, or climbing stairs redirects blood flow and adrenaline and can help.
• Urinate: If you feel the need, peeing sometimes helps relieve pelvic tension and can reduce an erection.

Options involving sexual release

• Masturbation to orgasm: If you are in private and comfortable doing so, masturbation and orgasm usually cause the erection to go away. That is a normal and safe option for someone who is 18.

What NOT to do

• Do not try to forcefully bend, squeeze, or injure the penis to make it go down.
• Do not tie or use constrictive objects around the base — that can cause damage.
• Avoid applying extremely cold items directly to the skin (wrap cold packs in cloth).
• Do not take extra medication (like more ED drugs) or use unknown substances to try to change the erection.

When to seek medical help (urgent)

• If an erection is painful or lasts more than 4 hours, go to the emergency room or call a doctor right away — this could be priapism and can cause permanent damage if not treated.
• If the erection follows a pelvic or genital injury, or if there is blood in the urine, seek immediate care.
• If you frequently get unwanted or prolonged erections, or if they are associated with medications (like some antidepressants, antipsychotics, or erection drugs) or recreational drugs, see your primary care doctor or a urologist to review possible causes and safer management.

When to see a clinician (non-urgent)

• If the problem is recurring and bothersome.
• If erections are painful even when not prolonged.
• To discuss medication side effects or interactions.

If you want, tell me more about when this happens (after sex, during sleep, after taking any medicines or drugs, with pain, etc.) and I can give more tailored suggestions.