My son who is 15 accidentally used testosterone gel will he be ok?

Yes. Brief exposure to testosterone gel should not produce any long-term effects. Call your doctor if the person develops enlarged genitals, premature pubic hair, increased libido, or aggressive behavior. Be aware that occassionally testosterone may be used by atheletes to increase muscle mass and it is reported up to 2% of teenage boys have tried steroids for that reason.
Yes. Reported adverse events from repeated secondary testosterone exposure in children include premature pubic hair development, advanced bone age, increased libido, aggressive behavior, and inappropriate growth of the genitalia. In most cases. The adverse event was usually reversed after removal of the testosterone.
Yes. Make sure it's washed off. If it was accidental and not for a long period his natural testosterone will transiently decrease for a short period of time and then kick back into normal.For more: www.Peedoc.Com @thepeedoc.
Yes. He should stop using it now but short term exposure is not going to cause any long term consequences.