It certainly won’t do you any harm to contact them. Even if you bother them slightly, it’s unlikely that the actual person making decisions will be the person handling your query in the HR department.
You can be creative too – e.g. tell them you’re going to be in the area and would like to call in for an informal conversation to learn more about the job. If it has already been offered to someone else, they’ll have to tell you. Another thing to try is tell them you’ve been offered something else, but would prefer to work for them so you’d like an interview A.S.A.P.
I applied for a job at the UN in December 2014 and the position wasn’t filled until June 2015, so in some cases, you might be waiting 6 months. I hope not for your sake. Good luck.