Ditto what FTMax said above. Sperm can only survive outside the human body for a couple of minutes, and whilst it's highly unlikely that anything happened, there is a small possibility that viable sperm may have made it to somewhere you don't want it to be.
It's not easy for anyone to fall pregnant even under the best of circumstances, but all it takes is one single sperm cell to make it to a viable egg & you're up the creek without a paddle. I'd recommend doing a test just to put your mind at rest.
I should also add: semen is a very risky substance in terms of STDs.
Obviously any form of penetration is more risky than handjobs, but you're at risk of catching an STD if an infected partner's semen comes into contact with any open wounds or with mucous membranes (such as where you were fingered).
So if you choose to move on to penetration, condoms are a must when playing with unfamiliar guys. You can't tell whether someone's clean or not just based on how they look, so please always use protection & get yourself tested regularly.
Enjoy your play... but please play safely.
