Mistakes are bound to happen. Here, you have already made a mistake by leaving a 24-year experience bank job and not knowing the reason. The new job may be quite challenging and, of course, monetarily beneficial. It is very difficult to judge a new assignment or organization within a span of 10 days. I suggest that if it is a reputed organization, you try to settle down, which may take 2-3 months. The feeling of discomfort is likely only because you spent 24 years in your previous role, and within 10 days, it is unrealistic to expect the same level of comfort.
If the position you have with your current organization, along with the monetary benefits, is extremely good, and if you have confidence in your abilities, it is better to continue with your present organization where your growth potential is unknown. Approaching the bank to withdraw your resignation may potentially lead to an uncomfortable situation, not immediately, but at a later stage, such as through a transfer, etc. These are only possibilities. Therefore, I suggest you accept the new job, and if you find it difficult to adjust later on, you can consider looking for another job with confidence in yourself.
All the best, and do not worry. These are all momentary challenges, and believe me, nobody fully adjusts to a new job in 10-15 days. Best of luck to you.