all little boys do this its quite normal at this age and doe'snt tend to be sexual, its more of a comfort thing and exploring their bodies, dont be shocked by it, we dont worry when babies suck their toes or or toys ect, they're learning everything like what does thisdo/noise doesit make/ whats this for.
Absolutely cliffsdoll. It's all part of the exploration of the body that all children go through - sadly it includes exploring their orifices at inoportune moments as well!
My daughter is 17 months old and started poking herself 'there' when in the bath. I did wonder whether I should be removing her hand as it just looks so wrong, but after reading the above I'll leave well alone!
Thanks jackie for asking this Q - it's helped me as well :-)