over pubic bone growing in size could be due to collection of blood which might get spreads due to effect of gravity. If it increases rapidly and warmth to touch, it indicates the possibility of get infected.
I suggest it to get it evaluated to rule out any infection. Meanwhile apply cold
packs over the bruise and you can take anti-inflammatory drug like motrin
to reduce pain and inflammation.
I do hope that you have found something helpful and informative and I will be glad to answer any further query.