Providing it is just the seal and not the actual porcelain bowl, you can fix it.
Have a good look at the pipework round the back, then go to B&Q, Wickes or a builder's merchant and buy the new bit(s) required. Most usually, its a rubber gasket that fails, due to old age perishing.
When you pull it apart, be careful to reduce disturbance the pipework so as to avoid breaking any other seals, further on. It could be rather messy, have a bowl ready to drop the dirty bits in.
Then clean up the pipe, remaining fittings and toilet outlet, with warm soapy water so the new stuff gets a good fit and reassemble it all with the new bits. Washup liquid helps it go together easier.