i would advice you to visit a dentist
immediately as the dimensions of the white patch
is quite big..firstly you should go for an OPG xray as it will give a clear picture of the positioning of your wisdom teeth.. this patch has been formed because of repetitive trauma caused due to malalignment of teeth..this patch may become infective any day and will cause lot of trouble as spreading of infection into other tissue spaces is quite common in such cases..it will restrict your mouth opening and you may feel pain in your TMJ
joint of that side also..this condition is known as pericoronitis
and becomes quite painfull...so my advice will be that you get your wisdom tooth removed as soon as possible...this white patch in the initial stages is a normal phenomenon but it may convert into cancer also in later stages if you dont get this treated for years.....
its scary to know but yes it is a possibility too...