I recently started a new position as a researcher in a start-up. This is the founder's (my boss) first start-up and it was created less than 1 year ago, so I would say we are both new at this. The research can entail a lot of involved mathematics (similarly to e.g. machine learning), but in the end we are of course concerned with practical deployment too.
Our first intern started a 5-months internship this week. His background is pure maths, and the internship we agreed on was very mathematical. After all parties agreed to the internship and its topic (though my boss was not very involved at that stage), a more deployment-oriented project came up and my boss told me that he would like the intern to work on it. This week, he made it clear that the main focus of the internship should be this project.
This change of plan makes me uncomfortable. I am personally somewhat agnostic to both internships (mathematical or deployment-oriented), but I find it unfair to sell an internship to someone and then change the topic to something he may not like, once it is too late for him to change his mind. On the other hand, my boss is the boss. What should I do?