Your friend either hasn’t told you the entire story or is lying. Viagra, Cialis, and other ED meds won’t cause your penis to burst - human blood pressure is insufficient to pop a penis like a balloon. What may have happened is a penile fracture, where the outer sheath of erectile tissue tears in response to physical injury. Typical drivers of penile fracture are situations that cause the erect penis to bend forcefully, such as falling on an erection.

Taking ED meds without ED will just result in a very firm erection that will likely persist awhile after ejaculation.