My gums were swollen yesterday but now it's gone. could it still be infected?

Possibly: Unfortunately, we can't diagnose your problems over the internet. You need to see a dentist who can personally examine you and give you an accurate answer. It could be as simple as some food caught between your teeth or under the gums, or possibly a more serious dental problem that needs attention. The only way to know for sure is to see a dentist.

Yes it is, but: There are bacteria still under your gums, but you are not as infected as yesterday, but it will come back. You need a better way to manage the bacteria. Look into the perio protect method. It has been shown to produce better results than deep cleaning (j clin dent 2012) and it killed 99.98% of the bacteria in the gum tissue j dent res 2007. Look up www.Perioprotect.Com for help.

Gum infection: Yes, an infection may be present. Swollen gums usually indicate gum and/or tooth infection. Sometimes the swelling will come and go. Do not assume an infection is gone. Visit your dentist very soon for an examination of the area.