Whether you can sell what you made depends on that implied licence or tacit permission discussed in this question. It is possible that you do have an implied licence to sell a garment made from a pattern written by someone else, but it is also possible that you don\’t. It depends on the circumstances. To be safe, you should ask the copyright owner for permission. In fact, many copyright owners and designers will have already answered this question for you, by including a notice on a pattern or in a book that the items cannot be knit for resale, or similar language.
You should not simply assume that because you have permission to make a copy of the sweater or afghan by following the pattern, you also have permission to deal with that work in any way, for example by selling what you made.
By way of explanation, subject to other contractual or licensing restrictions (for example, if licensing terms were imposed at the time of purchase of a pattern), a copyright owner cannot control what you do with the copyrighted pattern you acquired, but she can control the making of copies of her work (such as making the sweater or afghan, or photocopying the pattern). Because the copyright owner can control the making of copies, she can set what conditions must be met in order for you to have permission to make a copy. Whether or not you are permitted to sell what you made will depend on the terms of the implied licence the copyright owner has granted.
In short, the safe answer to this question is that you can\’t sell what you made, because you were not granted that permission. You need to contact the copyright owner to acquire that permission first.