piolat light to big?

i have a baxi bermudu fire with back boiler when boiler is not beining used the pilate light is always making a poping noise light ing gas about 2 inches away it i hold in the grey button that lets the gas out when lighting light its ok in conjuntion wit h sparking buton but soon as i let out grey button popping starts i have a good strong piolal light cant speel by the way any help well ombe as its cold in the mendip hills l