A pingle is the little tab of a jigsaw puzzle piece or some other interlocking tab of a similar nature. Or so it was in common use in my family throughout my childhood in the 1990s and early 2000s (Pacific Northwest, USA). In fact, I can't recall ever using the word pingle and having someone (family or friend) need my clarification as to what I was referring. However, the dictionaries do not corroborate this definition. Webster's gives a couple definitions, and Oxford a few more, but none of them is remotely close to the above use that I thought everyone knew. Has anyone else heard the word pingle in a context outside those given by the dictionaries?
The OED has several definitions of pingle, one of which one is similar to the definition given by @R.Dye in his answer, since deleted.
Sc. To exert oneself, work hard or laboriously; to struggle, esp. against adversity; to toil for a living. Chiefly Sc. a. intr. To strive, contend, vie; to quarrel. Also trans. with infinitive.
b. trans. To compete fiercely with; to vie with, rival. Obs.
Sc. To be hard-pressed; to be troubled, worried, or oppressed.
intr. Chiefly Sc. To work in a trifling or ineffectual way; to meddle or have to do with in a petty way; to waste time, dally. a. intr. Now Eng. regional (chiefly north.). To pick at or play with one's food; to eat with little appetite, nibble
b. trans. Eng. regional (south.). To pick at or toy with (one's food). Now rare.
A small metal pan or shallow cooking pot, usually having a long handle; a saucepan
A small enclosed piece of land; a paddock, a close
I offer this simply because pingle is a lovely word, and we should have the definitions on the record. I agree with @jlovegren that your meaning of the word was probably coined by your family.
Note: I need to clean this up, but have a plane to catch and I can't until early next week**. I will also look for definitions in a dictionary without a pay wall.
Could 'pingle' have been bastardized from 'pintle'? 'Pintle' and 'gudgeon' are the terms for the male and female parts of a hinge used for attaching a rudder to a boat or a shutter to a window frame. The analogy with the tab and slot on a jigsaw puzzle piece is obvious.
Probably the word was coined in your family or some other particularized context. If you are working on a jigsaw puzzle together with people it would be easy to coin vocabulary on the spot to talk about features of the jigsaw puzzle, because there is near-complete information. They can read your mind and then know what the word means, even the first time you ever use it.