Agreed.... the problem with sanding, is knowing when to stop. Who knows how well the first coat was applied. When trying to get all of the steel wool and bubbles out, you may end up sanding right through the first coat into the stain. And then, you're in a world of hurt for sure. This is unforgiveable.... you should get a complete re-do by the contractor.
Are you certain this contractor knew what he was doing? I'm surprised he used a product like Minwax on site. Especially an oil based product. That stuff takes so long to dry, in an un-controled enviroment (spray booth or clean finishing shop), the sticky surface will pick up all sorts of airbourne particulate. That may be the bumps you feel. Most contractors will use lacquer when working on a job site because it flashes off (dries) so quickly and is so easy to use. Or most certainly, something water based. Please don't tell us he used steel wool with a water based poly. If he did, whatever steel wool is left will start to rust.