When you want to talk about a present possibility, you can use could

Khalid isn’t in the office yet. He could be stuck in traffic
Why is that man on the ground? He could be injured
We missed the meeting. I think we could be in trouble with the boss Here he comes



You can also use could when you want to talk about a future or potential possibility
Don’t put that glass on the top shelf. It could fall off
If you don’t tighten those bolts, they could come loose
We should put away the patio furniture. Otherwise it could get damaged this winter


You can also use could have + pp verb when you want to talk about a past possibility

You shouldn’t have put that glass on the top shelf. It could have fallen off
If you hadn’t tightened those bolts, they could have come loose
I’m glad we put away the patio furniture. If not, it could have gotten damaged last winter