EDIT2: Yes, if you've transferred funds to the wallet then you have to wait for it to finish syncing. If there's no funds in it then I'd suggest switching to a lightweight client instead, you can always run a full node later if you want to help network security.
Yeah I transferred about 5 bitcoins to this wallet so I guess I have to wait for it to sync
If you really want to use those coins, you may upload your wallet to some online service, pay using those bitcoins, wait for your local copy of the blockchain to complete, regenerate a new wallet and send those coins back to your local wallet.