Oh dont worry.... a similar thing happend to me... it depends on how the plant broke... there is a technic called suppercroping which consists of bending the plant till it snaps in one spot and with time that branch will get back up and heal the wound... this allows for more budding sites to form and it also gives you a bigger and tastier bud on top of that elbow/crack....
here is a video of some guys supper cropped plant..
so basically if the part that broke is still somewhat attached to the rest of the plant.. give it a chance to heal... oh and this may cause your plants to flower a little longer.. i say for every crack/bend you make give it an extra 5 days to a week of flower.... but its seriously worth it...
I supercrop all my plants during vegging, and one more time when it enters flower....
On the other hand if you clearly broke the meristem off... dont worry... its not a bit problem at all..... you might wanna burn the tip of the place it broke off just to get any bacteria off... like when you burn a home sewing needle to stich someone up ... (not that ive ever done that)hehe
some varieties actually give a bigger harvest if you clip the meristem off .. the plants energy will be focused on the branch tips that havent broken off.......
i hope this helped you out a little... if youre really that worried about it.. try and post a pic and ill let you know what you could do next...
till that time....
keep it green in love and LIGHT IT UP!!!!