Is "an obstacle/obstruction against something" grammatically correct?
You are probably right in frowning a bit at obstructions, because it is more seldom used than obstacles, as you can check here
As for the grammaticality of your sentence, I think it is not incorrect. However, it might read better if you express it in this way:
There are two obstacles against young professionals trying to find a job in this field.
I do not know the rest of your sentence, but I am sure that one can find a way to fit this sentence in without a problem.