>>3489465You won't notice it much (if at all) in your pics, unless shooting wide open and against the sun, in which case you'll get more flare than normal.
That said, it needs to be cleaned because if you leave it it will only grow more and start etching the glass.
If you bought it off ebay/whatever and can return it, do that.
Otherwise try to clean it yourself. You won't find anyone willing to clean it for less than you could buy a new 50mm f/1.8.
If it's a manual focus lens, it's not hard. Google for some disassembly guide or youtube vid.