Green’s Dictionary of Slang

toothache n.

[euph.]

an erection.

[US]D. Lypchuk ‘A dirty little story’ in eye mag. 8 July 🌐 It looked like a real toothache, so she gave him a bit of punishment, playing the piccolo like a real Peter Puffer until she received Holy Communion.

In phrases

give someone a toothache (v.) [pun on SE; but note sense above]

to be ‘sweet’, e.g. he said you gave him the toothache.

[US]A. Heckerling Clueless [film script] cher: He said you gave him a toothache. tai: How’d I do that? cher: It’s an expression. It means he thought you were sweet.
[US]College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 Toothache (noun) [give a toothache (phr.)] Sweetness. [Act sweetly.].