first of all let me make you clear that erection is not associated with white spot and these are two different entities . your frequent erection may be just physiological and associated with your life style , too much thought of pleasure, watching pornography, thinking and even physical relation with your female counter part may all cause it. for this you must do some exercise and yoga
regularly and remain relax and avoid over consciousness of erection . you can get your BP measured and if required testosterone level
can be done.
your spot may be due to fungal infection
so it is better to get it examined by a dermatologist
and maintain good hygiene of your sex organ.
thanks for consulting HCM.