All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad (
) is His slave and Messenger.
Imitating or counterfeiting trademarks and brand names is not permissible, as it constitutes an infringement upon the rights of their owners. The sin of such transgression rests upon the one who engages in imitation or counterfeiting.
If a person becomes aware that such imitation or forgery has taken place, it is not permissible for him to purchase from the counterfeiter. This is the general ruling. As for your particular case, based on what you have mentioned in your question, there is no blame upon you in keeping those clothes.
Allah Knows best