Name spelling problem in recommendation letter I have applied to several US universities for admission to the PhD program this fall, so I requested my professors to write recommendations for me. 

One of the professor wrote my name incorrectly. My full name is: Md Rohan Hossain, but the professor wrote Md. Rahan Hussein. He already submitted the letter with that incorrect spelling. He completed the recommendation process online. 

In this circumstances what can I do? Will it cause a big problem?
Do not worry about this. Just use the letter and ignore the spelling mistake (which most people will consider very minor).

As long as it is clear that this letter was meant for you (which is the case here), you are fine. People will care about the content of the letter, not about really minor spelling mistakes in your name, address, etc.