It largely depends how much you want to get through that door today, how much damage and resultant cost you are prepared to face and whether those costs would be greater or less than getting a locksmith out tomorrow. Personally I'd put my size 10 boot to it, just by the lock but that stands a good chance of hurting your back. You could, of course, forget about it and the key will turn up one day. Before I had all new doors fitted we had locks on all internal doors. I kept a spare for each one in my office for just this eventuality because it was so foretellable.