Sometimes Joe is so attracted to Nicky and so overwhelmed by love that he comes way too quickly. Sometimes it happens several times in a row.
Would love to read all kinds of variations of this: Joe being embarrassed and Nicky being understanding, Joe laughing it off and Nicky teasing him, Nicky being flattered and Joe being like 'well I can't help it can I look at you,' Joe being apologetic and Nicky having to jack himself off quick to catch up, etc. etc. whatever you come up with