Sorry for asking this again,but,I just got a puppy today and I want to return it,am I being cruel?

Heya folks. Im just turned 23 yesterday. For a long time I've wanted a dog,and seeing as it was my birthday yesterday I decided to go out to a local dog shelter and paid a hundred quid for a male black labrador pup (he's got a bit of collie in him too). I live with my uncle (and so does our fourteen year old female cat). Now I knew that if I got the pup,my uncle would say no. So I hinted and hinted what I was up to to him for a few days,knowing that he is not stupid and that he would suspect me arriving with a puppy any time. Sure enough,I came home with 'ziggy' (the pup) today. My uncle was not pleased at all. He's barely speaking to me atm. The pup is currently nestled up beside me sleeping. But I've suddenly realised like I've made some big mistake. I don't think I can take care of this guy. Our house isnt big enough. I'm thinking of returning to the shelter tommorow and bringing him back. Is this cruel?Sensless?I feel rotten...please help:(