Question about ETH Block and Uncle

Someone else found the actual correct block, our block was correct as well, it's just that we mathematically found just after the other accepted block. In other words, someone else beat us in calculating the mathematical equation and propagating it to the network first. We still did the right job, we just did it slightly later. In other blockchains, such uncles are not rewarded and are orphaned. Lucky for the miners of Ethereum is that they get a partial reward nonetheless.

Ethereum has a high orphan/uncle rate, probably the highest of the all blockchains, especially due to the gas limit increase and relatively low difficulty leading to short block times.

Does it mean that we have to wait up to 2 weeks to find another block ?

Possibly. It's also possible that we find it any minute. Mining is a game of probabilities and statistics. You always have a chance to find a block at any given time. You never have 0 probability if you are mining. The probability increases with your hashrate. On average though with the current hash rates, we should find it every 16-17 days.