Frozen garage tap

Looking for advice if this is a problem!

My partner wanted to set up a skating rink in the back yard. They read they need to turn on the water and then turn it off after every flood for the rink.

The problem is… the first time they went to turn on the water to the garage the tap was already frozen. So they ran water to a frozen tap and Now the tap will have water in the pipe. They turned off the water and say there is nothing that can be done. But I think this is a problem. I’m worried it will now freeze and maybe burst. What do we do?