if you're already starting to feel better, i'd get back into it.

working out when you're sick is risky. sometimes, you'll start lifting and feel better cause of the endorphins, but then at the end of the workout, you feel 10x worse. there have also been other times when i feel better after i lifted and didn't feel as sick for the rest of the day. other times, it didn't affect me either way.

you won't find a definitive answer like you're looking for cause each person reacts differently to working out while sick depending on their immunity system, the kind of cold/flu they have, what they're taking for the cold (vit c, zinc, echinacea, etc), and there are numerous personal biological factors to take into account as well. the only answer is to find out for yourself what you can and can't get away with as far as working out when sick. eventually, you'll know when you can and when you can't, but it takes time and nobody else can give you the answer.