Yes completely normal!
With Abbie and Ella is was a sure sign they were teething. Not long after that they both get a really runny nose (not green) and that is when I know they are getting a tooth through. Katie misses out the runny nappy and goes straight to the runny nose when a tooth is cutting.
His bum may be really sore as well - all 3 of mine get very blistered bums (Abbie's is big open, and bleeding sores ) I've tried everything on their wee bums, but have found nappy cream from Bodycare for ¬£0.99 best on the market - works just as well as Bepanthan but quarter or price