I accidentally hurt a dog when driving. It was apparently beneath the parked car and I did not notice when getting in. It got hurt and limped away. I feel extremely bad for hurting it but could not do anything for it. I am not sure what to do but I feel inclined to give sadqah and repent. Please guide.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Whether or not you are certain that you harmed this dog, you are not required to do anything. You do not have to give charity or expiation as you are not sinful for what happened, because the one who does something by mistake is excused and is not held responsible for his act, as Allah Says (what means): {And there is no blame upon you for that in which you have erred but [only for] what your hearts intended.} [Quran 33:5]

Allah knows best.