On the couple of occasions that Avast has picked things up for me I've quarantined them (which removes the danger) then after a bit of thought about them have deleted them from quarantine and rebooted then run AV checker again to see that they are cleared.
I've always tried to calculate whether any side loss from deleting them is likely to be more problematic than the worry of having "them about". So far whenever I've deleted things like that they've gone away and no harm has been done to my files or system so far as I am aware. If the bit quarantined is only the virus reported by the checker and is not part of a bundle of material that you may not want to delete then removal is no problem. If in doubt keep the whole lot in quarantine - where it can do no harm but any beneficial items of info can be accessed by your system - until you know for certain what is involved. I'm sure many on the forum will give you much better advice than mine but I know there is nothing for you to worry about once you have quarantined things - the AV checker has done it's job