I accidentally burnt baby during his bath 😭

I was giving my 7 month old a bath in the sink with his bath seat. The plug can’t have been in properly and the water kept draining so I leave the tap running. He starts playing with the tap handle so I move it the side… can you see where this is going? He started crying and I didn’t know what was wrong until I realised and my whole world fell apart in those few seconds. He’s happy now but his bum and legs are still red (it’s been about 20 minutes) hubby took over as I couldn’t even look at what I’d done. I honestly can’t believe I could be so stupid. I feel like a monster. He has nursery tomorrow and I don’t know how I’m even meant to take him.