At some point in your guitar instruction this is actually gonna come in handy. What your doing is very close to whats called a "pulloff". A technique lead guitar players and fingerstylists use. If you have callouses on your fingertips, which I doubt if you just started it happens accidentally as the dry flesh gets caught on the string. Sometimes it could also be a fingernail getting caught there as well. As stated previously go slow and try to concentrate on lifting finger directly off instead of dragging it off. Also don't press too hard down on the string another common beginner habit we all did. As you lift off from that pressure the string will resonate.

Nothing to worry about right now. Your fingers are learning new positions. Keep at it.