It doesn't look like anything TOO serious. Some citrus leaf-miner damage I think, so remove leaves with the little mining trails. Some of the misshapen leaves are just damaged through contact damage which is quite common - unsightly but not detrimental. It looks a little under-nourished. I would give it a good watering, then give it a good fertilizer with some added epsom salts and iron. A regular fertilizing schedule will bring it back to health after a while.

Slowly introduce it to some good light, and make sure it stays warm enough with good humidity and it will be fine :)