If you have sexual images sent to you by, or of, someone under 18 you could be classed as having child pornography, if you send them on then you could be guilty of distributing child pornography.
These are serious offences and you could end up in prison or on the sex offenders register.
There's no way around this: Long-distance relationships can be difficult.
On top of the jealousy that can arise and the deep pains of missing someone you care about, living apart can make physical intimacy, well, impossible.
Lucky for us, the year is 2017, and the communication options for long-distance couples have come a long way from hand-written love letters (although that's still not a bad idea).