Try Out The First Spell, the Blood Refilling Charm

Harry tried the blood refreshing charm out on a few different things, noting the effects on each and scribbling them down on a scrap piece of paper. If he was going to eventually try this on himself, he was going to be thorough about his testing beforehand. The chairs cover in sap as does paper, quills apparently bled ink so long as they had been used before, something that would be useful for writing if nothing else, and when used on a stuffed goat lying across the room from him, absolutely nothing happened.

Harry, his attention span rivaling that of a goldfish, eventually succumbed to his temptation to try it on himself. It gave him an interesting tingle when he used it on his foot, and the same feeling apparel again when used on his leg... But this book (and chapter) were supposed to be all about sex, so...

Taking a deep breath, Harry aimed his wand and cringed to himself as he cast the spell, before he suddenly felt the incredibly odd sensation of blood rushing to his penis. He was easily harder than he had ever been before, his massive erection bulging obscenely from his robes. What the fuck he was supposed to do about this?