No boy,

you don't have to worry about the immigration officer in the entry port. To be in academically in good standing.......definately you should be 2.0 or above...not around too............so.....just be sure that Tobacco thing for selling to minor is not related to going and coming from nepal......let me tell u my experience in last december:

stay cool, be in line to get stamp in your passport and I2o while entering US........when your turn comes then just go ahead say Hello sir, they gonna greet you the same way........and they asked me how is going? then i was like Wassup? The officer told me Not much...then he just looked my I2o...and stamped ....and din't even ask more then this ......then he haned my paper back and told me "You good to go sir" i m like "Thank you".

then its over dude...........nothing to worry about.......stay cool..........don't let you heart be bothered........so.....go to nepal and enjoy and come back..........