A bulbous nose tip needs surgery to be reduced, however, threads inserted into the columnella (a high level of expertise needed or there will be many complications) or high G prime fillers such as Radiesse/ Ellanse (injected right at the tip under the skin) can help push the skin of the tip forwards and upwards.
It gives an illusion of a sharper and slimmer tip and may be enough for some patients. For those expecting a drastic improvement, its best to go for cosmetic surgical enhancement.