It is normal for you to get the blurry vision after immediately you take the warm compress because of the close and warming of the eyes. However, the blurry vision may be temporary. You could just wait for the moment and then you will get the clear vision. During this time, you should not rub your eyes. You could also use the eye drops to release the symptom and make your eyes become comfortable.
It looks like you are worried about the possibility that warm compress would lead to some blurry vision. On the contrary, warm compress could help with your eye strain, relieving your eye infections and traumas ,etc. But you should bear in mind that never get across the line, so you should not get too much warm compresses to your eyes for fun. Just take good care of your eyes, if something's wrong with your eyes, just visit a doctor and take relevant actions.
As far as i know, warm compress can help release strained eyes. It is good for eyes. And i never heard any side effects of warm compress. So, your blurry vision may caused by other reasons. For example, poor eyesight and strained eyes and eye infection can also cause blur vision. Just visit an doctor and take an eye exam so as to know what makes you vision blur. Good luck