import re
s = """some text here 45 [check {xyz}]
more text 12 [check {pqr[25]}
some more text 56 [check {efg[4]}]
still more text 78 [check { jkl[12]}
more text 123 [check abc]
more text 34 ghi
"""

regex = r"(?<=check )(?:{[^{}]+}|[^\[\]]+)|\w+$"

l = re.findall(regex, s)
print(l)