That is probably WHY he slept, my DS always slept well while recovering from needles.
We had a not bad night in our house, kids went to bed about 2 hours later than normal, got up 1x to DS, gave him nurofen and a drink of water (he is teething) he went right back to sleep in his own bed (unheard of LOL) and then noone came into my room until 6:25am! With DH away, I got the whole bed to myself, instead of squeezing 4 of us into it like normal!