Driving with different tyres

Hello,

I have just bought a car, a Peugeot 207, and I have realised the size of the tyre on the spare wheel is different than the 4 tyres that are on the car at the moment.
On the car it's 185/65R15 88H
and on the spare wheel it's 185/60R15 88U

will it be a big problem to drive my car if I get a flat tyre and I need to use the spare wheel?
is the difference a big issue?
If that does happen I would probably use the spare wheel until I buy a new tyre in which case I would buy the right size.

Thanks.
Al