Forgot to burp prior to oil change

Have stopped what?  Draining?  

If you burp it will push a bit more oil into the tank, but that should be a fairly small amount relative to what was in the tank.  Like, less than the flat area on the dipstick

I gather that you did not burp the engine to evacuate the old oil from the crankcase and then drained the oil.  No big deal as long as you did not move the prop. A little extra old oil will remain in the crankcase due to your not burping the engine prior to draining out the old oil. Just be careful when you add the new oil to account for the slight amount of old oil that remained in the crankcase.  If you moved the the prop after draining the old oil but before adding the new oil it is possible that you may have introduced some air into the oil lines -- in that case a purge of the oil sytem may be warranted. 

Like David said it won't hurt anything. The only issue may be that if there was a liitle too much in the case then it might over flow the tank. If you do happen to have a little too much oil just drain off a tad from the bottom of the tank. If it isn't too full then don't worry about it.

Well shoot! I did move the prop and even had the plugs out. Did get a small amount of oil out of the bottom left plug hole. Did not remove the oil filter yet. Sounds like a purge required huh? 

Kenneth, maybe not. First let’s clarify everything that follows is my understanding based upon what I’ve been reading in the Rotax manuals.  I want to discuss “move the prop” and an “open oil system” before you think you need to purge.  If you ever rotated the prop in the opposite direction of specified normal rotation, and there’s a number of rotations called out by Rotax, but that number escapes me right now, you may have induced air into the oil system and a purge is required.  That’s regardless of whether the oil system is open or closed.  If the prop was rotated in the correct direction of rotation, if any spark plugs are removed, this matters not, as the oil system is still closed unless- the oil filter was removed at the time you rotated the prop, then even if the prop was rotated in the correct direction you would have an opened oil system and a purge is required.  But hey, when in doubt, purge.  Roger or Bill, please weigh in and correct me if I’ve misspoken. Edit: I just realized that if you did rotate the prop with the oil reservoir drained, you certainly could have sucked air into the system...