It could be overactive imagination, and if its an std, its not from that encounter, since you wouldn't get symptoms that soon.
Make sure you are drinking enough water, and not too much caffeine or alcohol, as this can sometimes cause an itching or burning inside.
If it persists, get it checked by your doc.
AJ
Let me also add there is no burning sensation when urinating or after any other ejaculations since then (masturbation), the "inside" of the penis (urethra) doesn't itch. This was a chance encounter that lasted all of 15 minutes, no foreplay, no oral sex etc. Pretty much just put on the condom before penetration, had sex for 10-15 minutes and then ended. Nothing else. I'm a bit nervous due to the slight itching / tingling. Not sure if it's my overactive imagination or what. Thanks again.