My PlayStation 3 disc drive is unresponsive!

Basically, my PlayStation 3 (slim) was loud. After being on for a couple of hours it sounded like a hoover, I didn't even know devices could get that loud. It definitely needed cleaning so I took it upon myself to open it up and dust it...it was extremely dusty. I followed a YouTube tutorial and did everything as illustrated. I only took large things out, I didn't take apart any components and I left the fan alone and just cleaned it as it was sat there. The only component I messed with was the drive, but I only took the silver plate off the top, that was all, I placed it back on when finished dusting. However, when I re-assembled my PS3, and powered it on, the disc drive made a strange sound, like the disc was trying to eject but it couldn't (I did all this whilst a disc was in the console, which I probably shouldn't have done). Now whenever I press my eject button it just beeps three times, like a disc isn't in there. I'm adamant nothing is broken, I was very careful taking everything apart and I've been inside it again and checked everything is okay, which it is! I'm sure I've just missed a detail or something of that effect. Any help or suggestions would be great, thanks!