I haven't heard back from you, and I apologize for any mix up in communication.
Lumps on dogs, especially Labradors, are fairly common. The ones that are moveable with the skin tend to be Lipomas, which are benign growths of fat. Other skin tumors can be cancerous and have a similar appearance. Mast Cell Tumors are common, cancerous, and look like lipomas.
Your vet can perform a needle aspirate, where he takes a small needle and gets a small sample of the tumor to look at under the microscope. He can then tell if it's nothing to worry about, or something suspicious that should be removed.
You could alternatively just watch the growth for any change in size or appearance. If it rapidly increases in size, have it checked.
And even a benign tumor can cause problems if it is in the wrong spot and interferes with walking or laying down. In that case, it would be removed.