You probably should have put it in the Avast Virus Chest. You do not tell us what file(s) where infected or where the infection was located. Is your machine safe? Hard to say with limited information.
I suggest you update your Avast definitions, make sure you have the latest version of Avast, and run a Quick scan. If an infection comes up, put it in the Virus Chest where it is safe. Keep it in the Chest for several weeks; you can always rescan it from the Chest after getting Avast virus updates. If it turns out to be a false positive (FP), you may be able to restore it or delete it from the Chest. Once you delete it, if it was an important file that was needed for your machine to run...you're out of luck.
You can also upload files from the Chest to Avast to have them check for FP. This is done during the next virus definition update.
Please run another scan and report back on your findings and let us know if you have any questions. Thank you.
