Remember that the lump is a result of a blow, and the blows very good cold. Accordingly, to remove a lump on forehead can help the ice, or rather ice pack. In order to do that, take a clean gauze or bandage. And best suited towel. From the refrigerator, remove the ice cubes. If not, then as a replacement suitable package with ice water. During the filling of the package need to be careful and watch that he does not leak.
After that, wrap the ice pack or ice in a towel or a thick layer of gauze (bandage). That is a thick layer necessary for soft and obligement compress, and also to the head was not very cold, in order to avoid colds.
Attach the resulting compress to the lump and area around it. Done actions will help to eliminate the bump in a relatively short time.
If on hand at the right moment, nothing of the above, try to attach to the shock of something cold. Maybe the bag will be a bottle of cool mineral water or frozen foods. Of course, whatever it is, it is desirable to wrap at least in a handkerchief, if there is nothing more appropriate.
In the case when this does not happens to be nearby that can help in the simple nickle in your wallet. The alloy of the metal of which it is made, has a positive effect on place of injury, and he's cool. Attach a Nickel to the injury site, and the bumps should not appear.
However, if the blow was too strong, and the lump is very large, it is better to consult a doctor in order to avoid concussions. Let him examine your head and tell you what to do.