disposal of shares : could I be in trouble ?

Hi, I 'm a French national living in the UK and I'm resident here for tax purposes. In the 2020-2021 tax year, I had to sell the shares that I had at my bank in France in order to gain some liquidity as Covid was happening. In total I received the equivalent of £9,000 following the disposal of the shares...an amount that was, at the time, below the annual exempt amount (of £12,300, if I'm not wrong : https://www.gov.uk/guidance/capital-gains-tax-rates-and-allowances) for the capital gains tax. The problem being that I didn't declare it to HMRC (to be honest, I asked this forum at the time and I'm pretty sure I was told that, because I was below the thresold, I didn't need to do anything...) whereas I apparently should have. That's what I was told more recently. And now I'm a bit scared. Would I owe money to HMRC and how much (I need to be prepared) ? Would I have to pay tax on the £9,000 (even if they were below the annual exempt ?) and of how much ? Would I have to pay a penalty for not declaring the amount (even, again, it was below the thresold?) and of how much ? sorry, I'd just need to have an idea of what I would owe HMRC potentially, many thanks

Hi J G,
If the actual disposal value was more than £49200 then a tax return would still be required even when the actual gain was below the threshold.
If not, then you do not need to do anything.
Thank you.