Section of tarmac missing near manhole cover deep

There is a approx 30cm x 25cm x 15cm+ deep section of tarmac missing near a double drainage/l cover in the road near to the cottages one after Rose Cottage - it’s been like this for a few weeks but is getting gradually worse - left hand passenger side tyre makes it rattle and looks like now it could collapse it’s as if a whole section around the cover is missing - if someone walked across the road here at night they would get a foot stuck here now - dangerous by the car cover - saw the road sweeper drive over this morning and it dipped to the side when it hit it - I was coming back from Eastern Leisure - it’s on the side travelling to Cardiff