My employer is moving in a new direction for which I seem to have been picked to be the (de facto) consultant for everyone else in the building. I have no official title or position that indicates that shift in responsibility, I'm still a level 1 grunt, I just have a different background that makes me more familiar with this new direction. My position of subject matter expert is a de facto position not recognized in any way by the company, it is just a matter of convenience for my coworkers to be able to ask me instead of taking the time to ask someone in our offshore office, who are officially recognized as being the people to consult for this new system (we have to wait at least a full day for a response).
I don't mind helping wherever I can, but the problem is that I also have my own workload and am lagging behind on it due to the amount of queries I receive concerning the new initiative. I understand that as a whole, it would be better for one person to be blocked if it means that 25+ other people are not, but at the same time, I don't want to seem like I'm making excuses to my management when I say "I had to help team members x,y,z and w with the new product" as an explanation to why my own work is done. I've come to the conclusion that I'm going to have to start turning away (at least some of) the requests of this nature in order to get my own work done, but I don't know how to do that without making people upset and getting a reputation of being unhelpful.