I'm doing a trip around the USA and I want to go see Toronto and Montreal from Chicago and then leave to Boston. I would be in Canada for only 3 days. do you think I might have any problems on my way back?
I have a B1/B2 (tourist) visa.
Going to Canada from a short trip while visiting the USA is no problem. Your USA visa won't help you get entry into Canada. You may require a Canada visa. Polish citizens with biometric passports don't need a visa, but ones with non-biometric passports do. http://www.cic.gc.ca/english/visit/visas.asp?country=poland1 and http://www.cic.gc.ca/english/visit/visas.asp?country=poland2
Please note the USA will include the days you were in Canada on your I-94. So you will have to leave the USA within 90 days of entering, your Canada trip will be counted as part of that since it is a short trip to Canada. https://help.cbp.gov/app/answers/detail/a_id/1218/~/automatic-revalidation-for-certain-temporary-visitors
I don't see any problems re-entering the USA. Even if your US visa has expired. The US visa is only useful til point of entry after that the I-94 trumps it and decides how long you can stay in the USA.