Can this rim damage be fixed or do I need a new rim? I somehow managed to ride over a screw that pierced through my tire and was long enough to reach the rim. It scratched the rim a few times (for as many wheel revolutions that it took me to stop the bike); see picture below. When I put my finger over the scratches they feel quite rough which will certainly not be good for the tube I imagine. Is there any way such damage can be fixed without having to replace the rim?
In the photo it looks like you have damaged the rim tape, not the actual rim. You should be able to replace it without touching the rest. The tape on photo says tubeless ready: if you are planning to go tubeless you should replace it with similar one, but if you plan to use tubes, any high pressure tape will work.