This Is a very painful experience I'm sure most guys have gone through,walking becomes a problem and adjusting yourself could be painful. It is called 'BLUE BALLS'

Do you know the connection between blue balls and
sex? Have you ever heard someone ask you, "What
are blue balls?" "Blue balls" is a slang term referring
to testicular aching that may occur when the blood
that fills the vessels in a male's genital area during
sexual arousal is not dissipated by orgasm.
When a man becomes sexually excited, the arteries
carrying blood to the genital area enlarge, while the
veins carrying blood from the genital area are more
constricted than in the non-aroused state.
This uneven blood flow causes an increase in volume
of blood trapped in the genitals and contributes to
the penis becoming erect and the testicles becoming
engorged with blood. During this process of
vasocongestion the testicles increase in size 25-50
percent.
If the male reaches orgasm and ejaculates, the
arteries and veins return to their normal size, the
volume of blood in the genitals is reduced and the
penis and testicles return to their usual size rather
quickly.
If ejaculation does not occur there may be a
lingering sensation of heaviness, aching, or
discomfort in the testicles due to the continued
vasocongestion. This unpleasant feeling has
popularly been called blue balls, perhaps because of
the bluish tint that appears when blood engorges the
vessels in the testicles.