I have a lump on the bottom of my tongue. it's not painful and it has what seems to be a white head, the color of plaque. should i worry?

Don't panic: The area below the tongue has a high density of salivary glands. Sounds like you may have an occluded salivary gland. Sometimes these occlusions clear on there own with salivary secretions. They tend to occur when you are dehydrated. Drink lots of water. And see your dentist for an examination of the bump

See a dentist.: I can't see your tongue, so my best advice is to make an appointment and see a dentist or a physician. Some lumps under the tongue are normal anatomy but there are other lumps that need attention.