but words hurt worse.....
for bones will mend, but words can never be taken back.’
'I know you are but what am I'
-Pee Wee Herman "Pee Wee’s Big Adventure" (he had an uberly epic bike!)
It is uncertain, but 'I know you are but what am I' may date back at least to the 1970s, as reported in Lee Thayer, Communication.
It is a rhetorical question, colloquial, childish. Assertion that an insult made by the party to whom the phrase is directed is actually true of that party, and not of the person using the phrase. Usually considered to be a playground taunt.
From me comment- Works as a feeble [or amusing] last resort, and if repeated continually can either #1- cause the person to give up in frustration #2- both break down in laughter [best result, but least likely] #3- end in broken bones *see ‘sticks and stones’.)