捏一把汗 (niē yī bǎ hàn, 'squeeze a handful of sweat') means to be nervous or worried for someone — like watching your friend on a tightrope. 真为你捏一把汗 = 'I was sweating bullets for you.'
Hand radical — left-side form of 手. Pinching, pressing, or moulding with the fingers is a hand action, so 扌 marks 捏 alongside 抓 grab, 推 push, 拿 take, 抱 hug.
Top-right element. Combined with the 土 below, the right side forms 圼 (an obscure phonetic niè), giving 捏 its sound. The 日 here is graphic only — there is no sun semantics; it is half of the niè-phonetic stack.
Bottom-right element of the niè-phonetic stack. Clay-pinching imagery fits neatly: 土 is earth/clay, the very thing one pinches and shapes by hand. Together with 日 above, 土 completes the phonetic 圼 niè ≈ niē.
