Is there an adage in English for "realizing you are not the biggest"?

There is an adage in South Asia which literally translates to: A camel has finally seen the mountain. Which basically goes back to a story where a camel used to think that it was the tallest until it sees a mountain and it realizes that it isn't and there are things taller and bigger than it.

Here is an example usage: BlackBerry used to think they were the biggest in cell phone market until they saw Apple; the camel has seen the mountain.

Is there an expression in English for this?

There’s always a bigger fish conveys a similar concept:

No matter how large or intimidating a person or thing is, there is likely to be an even larger or more intimidating person or thing somewhere.

(Wiktionary)

There is a question on Quora asking for the English translation of this from Hindi.

It suggests a couple of other idiomatic English versions, such as:

• someone has been cut down to size

• some one has been shown his place

I'd like to add (for reference, for future visitors) a couple that were more common, at least when I was learning to read:

• he has been taken down a peg (or two)

which I always thought referred to the traditional "ladders" used in school sports (including chess) clubs, but according to t'Internet might refer to the naval practice of pinning colours at varying heights depending on the status of the vessel's commanding (or ranking) officer.

and the older but still reasonably common

• been knocked off their pedestal

although neither of these really captures the sense of discovery inherent in the original adage.

But please go and vote for @lph's answer.

The following phrase is something that approaches closely the translation that is sought. It implies the possible understanding of an equality but superiority is taken into account as well (ref.).

• He had met his match. (She had met her match.,…)

The Free Dictionary

A rude surprise. The fastest camel in Giza tried out for the races in Cairo and got a rude surprise. When BlackBerry saw what the iPhone could do, it was a rude surprise to them. It's most commonly used in future tense: if that camel goes to Cairo, it will be in for a rude surprise.

The first usage I found was an article "A rude surprise could be awaiting Trump". It suggests he thinks he's been making a very strong court case, but that his efforts have actually been making it very weak.

The "rude" is very idiomatic. It's more like a traumatic surprise, but that doesn't have the same meaning. A rude surprise suggests the target has a great deal of pride, hubris even, and finds out they were very wrong.