The only time you MIGHT get into trouble is if you photocopied the pattern in large amounts and sold them as your design. It would be an extremely rare occurrence to even get in trouble for making an item from a pattern and selling it (you would have to be selling a huge amount to even be noticed). It is a courtesy and good form to give credit to the pattern maker if you are making their items - but it is not technically required. Most of us who make something we have seen on pinterest or in a magazine have put our own twists to it, be it color choices, small changes, something that has made it our own. And, lets say you were making and selling hundreds of an item that you originally saw somewhere and that person happened to see it. It would be on them to show that you actually took their idea or pattern to use. I would say that would be close to impossible to prove.