The risk here is very low. Sperm in precum needs to stay moist and reach you quickly to have any chance of causing pregnancy, and finger contact alone rarely allows that. It isn't zero though, so it's worth watching your cycle over the next couple of weeks.
Next Steps
If your period doesn't arrive on time, take a home urine
pregnancy test about 2 to 3 weeks from now for an accurate result. Otherwise just track your next cycle as usual.
Health Tips
If this is causing you a lot of anxiety, please consult your gynaecologist soon, since options exist to address it only within the first few days.