There are less chances for a heart disease
to present with a lump in throat.
But do get an ENT consultation and an Electrocardiogram done.
First to rule out the lump as there should not be any hard lump in the neck. there can be some other underlying disease .for lump you can get done an Ultrasonography
For heart disease initially Electrocardiogram would be the basic investigation to rule out any disease and it is non invasive also.